The shift from “media” to “social media” in the digital age has implications for processes of identity formation during adolescence and the transition to adulthood. First, the Internet provides young people with opportunities to co-construct entertainment and social environments tailored to their own needs and interests. Second, adolescents' presentations of self take place on the same screens and in the same activity settings in which they access commercial media programming. These changes reflect increasing cultural emphasis on personal agency and self-expression which brings to bear new tasks for identity development during the transition to adulthood that involve both opportunities and challenges for creating a coherent, stable, and meaningful sense of self. In terms of opportunities, social media give youth enhanced control over presentations of self in social interactions and increased access to social information and large networks of others to solicit feedback and reify self-concepts. However, social media also bring new demands to negotiate heightened pressure to perform a socially desirable self in a commercial environment that bestows value on attractive images and popularity. Suggestions for future research include methods that bridge youths' offline and online social contexts and that balance enthusiasm for the massive quantities of data that can be aggregated via data mining technologies with qualitative work that examines the lived experiences of adolescents' everyday social practices.